What type of data is it?
We capture LIDAR (or laser scanning) data which is a "point cloud" of XYZ data points. Our vehicle captures typically 24,000 points per second as it travels the route. The XYZ coordinates of each data point we record are supplied along with a reflective intensity value. Each point will be classified into a point class.
What are point classes?
In our database, each XYZ point has an additional attribute called "point class" so we can organise and view the data by class. We have special software that can find the ground surface in the "point cloud" data. Each point that is on the ground is put into the "ground" class. Once we have found the ground points, we can classify other points by height above ground.
Data is supplied in the following classes:
| Class |
Name |
| 2 |
Ground |
| 3 |
Low vegetation (0 to 0.3m above the ground) |
| 4 |
Medium vegetation (0.3m to 2m above the ground) |
| 5 |
High vegetation (2m and over above the ground) |
Is there colour data?
Currently we can only colour the data by intensity, which looks a bit like a black and white picture. By the end of 2006, we will have finished implementing a camera system so that geo-referenced digital images will be available too.
Using the ground points, it is possible to create a textured terrain model using geo-referenced airborne photography from another source.
What format is the data in?
Data is supplied in LAS 1.1 format. This is the standard format for laser scanning data. Further technical details can be found at www.lasformat.org
What coordinate system is the data in?
Ordnance Survey UK National Grid OSTN02
What is the accuracy of the data?
The relative accuracy is 30mm. This means you can measure point to point within the data (over a distance of up to 400m) to a 30mm accuracy.
The absolute accuracy varies from 30mm to 1m and depends on the GPS conditions at the time of the survey. This means the whole trajectory may be shifted but the relative accuracy is still maintained. An estimate of absolute accuracy is given for each block of data.
What data is available?
Coming soon.
What if I want data that is not yet available?
Please contact us at data@realitymapping.co.uk and let us know your requirements. If our survey vehicle is nearby, we might be able to capture some extra data to your requirements.
How can I view or use the data?
There are a number of free or low cost viewer software applications available. We have listed the main ones below:
Viewing and Analysis software:
Digitising, Modelling and Analysis software:
The data downloads are compressed in a RAR format. How do I uncompress them?
The data has been compressed so that it is quicker to download. Most compression utilities will be able to unzip the RAR format. A free compression utility can be found at www.extractnow.com.
What if I want a 3D model rather than laser points?
Extra modelling work is required to create a 3D model. Prices are dependant upon specification. Please contact us for more information.
Is there some demo data available?
Yes, rural and highway data sets available for download here.
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